<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    input:checked {
      outline: 5px solid red;
    }
  </style>
</head>
<body>
  <h2>11.html</h2>
  <form>
    <input type="checkbox" id="hobby" checked>
    <label for="hobby">css</label>
    <input type="checkbox" id="hobby">
    <label for="hobby">html</label>
    <input type="checkbox" id="hobby">
    <label for="hobby">js</label>
  </form>

</body>

</html>